Bad and unprofessional service

<p>I am on a top up contract with mtn,I pay R502..however on my invoice for july i was billed R732.83..When i checked its for self service reccuring data bundle,according to my understanding when you are on top up contract when your minutes are finish you can recharge, this morning I called mtn customer care 808,i spoke to some guy and he promised to escalate the matter for me and he said it's mistake and he is going to credit and send me a ref number,I waited about 3hrs but no ref number and I didn't get his name,I called again to do a follow up and spoke to thabile she placed me on hold then released the call,then I called again spoke to phumzile she said I have a credit on that allows me to buy data from it what I fail to understand why wasn't I told and why should a top up account have a limit allocated,I have Been an mtn for 4 years on contact and never have I ever experienced such bad service,I want my money credited back on my account.</p>